Rheostat



y tegrally formed means, which in addition tol Patented Dec. 17'1'929ERNEST' -A.'Bo1=ILMAN, or'oIIIoAGo, ILLINoIs, AssIGNon 'roIIELLoGGsWIfrcHBoAnn AND SUPPLY coMrANYyoF CHICAGO. ILLINOIS, aVCORPORATION or ILLINOIS RIInosrA'r Application ledl'an'uary 11, 1926.Serial 110.186,402. n

My invention relates to rheostats for varying theresistance 'in anelectricalciri cuit and [is adaptedparticularly for use in controllingthe current in the filament cir-.-k

cuits of electrontubes. Anobject of my invention is to provide arheostat that `is simple in constructionbut very durable and reliable inis operation. y A feature of my invention is the provision of a novelwiper arrangement in which the wiper, which engages the convolutionsofthe resistance unit, is provided with inf providing yi'rictional meansfor maintaining the wiper in any of its adjusted positions, forms awiping contact, positive in itsoper-y ation, between. the wiper and theconducting member VVwhich electrically connects the wiper with oneterminal of the rheostat. This construction provides a positiveconnection betweenfthe Wiper and the conducting member and assuresapositive electrical wiping contact.

l The above and other features will be Amore vparticularly pointed outin the ensuing specifcation'and the appended claims. For

a more complete understandingof'the same reference may behad to theaccompanying drawing Vin which like reference characters denote likeparts and` in which; Y Fig.v 1 is a. front view of the rheostat of myinvention.

Fig. 2 isa right side view of Fig. `1. Fig 3 is a rear view of therheostatof my invention, illustrating it in one of its actuatedpositions.

, Fig. 4 is a sectional view 4 4. of Fig. 3.. Y Referring now more indetail `to my invention, as illustrated in the accompanying 'along theline drawing, it comprises aresistance unit or4 coil 2,l `which may be:of any predetermined ohmic resistance,"woundpby a suitableAmachineup'on a flatwstrip of insulating matef rial The ends of theresistance unit `f2 are held in place by being passedthrough suitableorifices in the strip 3. After Vthe coil 2 has beenvwound upon theinsulating material 3, theV Whole isformed into a substantially ringshaped member R by means of a suitable forming operation. o f

The bakelite or porcelain basel is providedk with a peripheral'rim 23which forms 6 and 7l toclamp thev parts in position.` The terminals 2O.and 21 are for the usual solderedconnections and the nuts 16 and 17provide' means for clamping conductors to the screws. 6 and 7 ywhenl theterminals 2O yand 21 vare not used. One endl 22 of the` resistance coil2 islsecured to the screw 6 other end 22 of coil 2 is secured to thestrip 3 by passing the same through an orifice .provided for thispurpose inthe end 8 of theA insulating strip 3. v

4.The screw7'passes throughy the base of yan arm 24 Aof conductingmaterialwhich terminates `at itsopposite end in ay circular plate 25.Plate25 has acentral orifice of a size to fit loosely around a shaft 31which,

extends through a ferrule 26 which rests in The ferrule 26 has'itslopposite ends upset The part of the shaft 31 which` extends through the`ierrule 26 is reduced to provide a shoulder which restsagainst theturned up end 30 of the ferrule 26 and prevents inward longitudinalmovement of the shaft 31. A

knob K is attached tothe end of the shaft" '311,:rotatingthe shaft andits' associatedparts.v

For a detailed description `of the method `used to support the knoblKreference may be had to Patent N o. 1,678,524, issued to Emil`lrNielsen, July 24, 1928. The other end ot the shaft 31V extends beyondthe face 10 of the yto which is joined the Vterminal 20." The `asuitable orifice in the vhub 1 formed in-` i x 'teg'rally with base 1.

V" against the face 10 oftheintegrally formed Ahuh 1. and the facek 12of the base 1 as shown int grally formed hub for purposes hereinportion33 which has its edges a and b slightly turned up so as to facilitateits movement across the turns of wire which comprise the resistance unit2. The Wiper 32 is so formed. as to provide a spring effect for grippingthe convolutions of the coil 2, to assure a good contactual engagement'between the end 33 .ofv the wiper 32 and the convolutions of the coil2. An arm 34 a suitable size and material is secured to wiper 32 by thetwo depending legs c and E which are so spaced as to snugly receive thewiper 32 therebetween.

The wiper 32 is also provided with Yan integrally formed dishedsemi-circular portion 3,. the portion 32 and the arm 34 having suitableorifices of a size to lit over the reduced end portion 31 of the shaft31, which is then spun over firmly to secure the wiper 32 and the arm 34on the reduced end portion 3l.

The dished semi-circular portion 32 is split into sections e which arebent down in order to provide a better Contact with the circular plate25ct the arm 24; thus providing' trictional means to hold the wiper 32in any of its adjusted positions. The arm 24 is so formed that it has atendency7 to spring away from the face 10 of hub 1'.; thus maintainingthe circular portion 25 in good contactual engagement with the legs e ofthe wiper 32. The arm '2-1 electrically joins the Wiper 32 to the terninal 21 of the rheostat.

The porcelain or lbakelite base 1 is also provided with an integrallyformed lug 40 which engages the panel to which it is mounted. An orilice36 is provided as a means for `mounting the rlieostat and a mountingscrew is inserted in the orifice 3G and a suitable orilice provided inthe panel. A nut is then threaded on the screw and this serves to holdthe rheostat in its proper posi'- tion upon the panel. An integrallyformed lug 37 is provided on the porcelain base 1.to ac3 as a stop forthe wiper. end 33 when in its normal or extreme advanced position. Aninsulating washer 38 is mounted between the end 8 o the strip R and theturned over portion of the connecting strip 24 to prevent the strip 2-lfrom contacting with the end of the winding on the strip R, and also toserve as a normal resting place for the Ywiper end 33.

Having described the apparatus which coniprises the rheostat, l willnext give a description of its operation. When the Wiper end 33 rests onthe insulating washer 38 the rheostat is in its normal or olf positionand no current passes through the resistance coil 2. Vhen the linob Kisturned the shaft 31 `rotates and with it the wiper arm 32, and themember 34, the flared end vof the Wiper arm 32 passing into engagementwith the peripheral face of the resistance coil 2. This completes anelectrical circuit from terminal 20 to terminal 2l by the way of screw7, arm 24, circular plate 25, depending legs e, wiper 32, flared wiperend 33, resistance coil 2, screw 6 to terminal 20. As the wiper 32 isrotated the amount of resistance in the circuit is lessened by the wiperl32 reducing `the number of turns of wire on the resistance coil 2between brush 33 and terminal 20 and consequently a larger amount et'current is allowed to pass through the circuit. The wiper 32 mayberotated unti it reaches the end 22 ot the resistance coilv 2 where itcomes in contact with the integrally formed shoulder 37 of the base 1.lVhen the wiper is in such a position practically none of theconvolutions ot wire are in the circuit and the maximum amount ofcurrent is passing through the circuit.

W'hile I have described a particular embodiment of my invention it 1s tobe understood that I, do not wish to be limited to the exact structureillustrated and described, but intend to cover all changes andmodifications which come within the spirit and scope of the appendedclaims.

Having described my invention what I claim as new and desire to secureby Letters Patent is:

l. In a rheostat, a supporting base, a resistance element mounted onsaid base, a hub integral with said base, a shaft rotatably supported bysaid hub in said base, a wiper secured to said shaft by an upsettingoperation and arranged to traverse said resist-ance element uponrotation of said shaft, said wiper having an enlarged portion comprisinga plurality of dependinfr legs adjacent said shaft, a terminal on saidbase and a resilient arm having one end iXed to said base, the oppositeend. of said arm being held {irmly in engagement with lthe dependinglegs of said wiper, said engaging portions of said arm and wiper beinglocated on the same side of said hub, said arm electrically joining saidwiper to said terminal and Preventing longitudinal movement of saidshaft and also operating frictionally to retain said wiper in adjustedposition due to the resiliency of said arm.

2. In a rheostat, a supporting base, a resistance element mounted onsaid base, a shaft rotatably supported by said base, a wiper secured tosaid shaft by an upsetting operation and arranged to traverse saidresistance element upon rotation of said shaft, said wiper having anenlarged portion comprising a plurality of depending legs, a terminal onsaid base and a spring arm having one end `fixed to said base, theopposite end ot said arm being held by its resiliency firmly inengagement with the depending legs ofsaid wiper to prevent longitudinalmovement of said shaft, said'arm and said wiper engaging each other onthe same side ofsaid supporting base.

3; In a rlieostat, a supporting base` re-V sistance element mounted onsaid base, a shaft rotatably suppoited by said. base, a

Wiper fixed to said shaft by an upsetting operation and arranged totraverse said resistance element upon rotation of said shaft, said Wiperhaving an integrally formedenlarged portion comprising a plurality ofdepending legs,`a terminal on said base and an arm having one, end iXedto said base, the opposite end of said arm being held vresiliently inengagement with the depending legs of, said Wiper, said arin and saidWiper engaging each other on thesaine side of said supporting base, saidarm ele'ctricallyvjoinf ing said Wiper to said terminal and also actingfrictionally to holdsaid Wiper and shaft in their variousadjustedvpositions, and serving as means to prevent V longitudinalmovement of said shaft. y l 4 Y v,LIn a rheostata supporting base, are*sistance' element mounted on said base',a

kshaft rotatably supported by saidbase, a

Wiper secured to said shaft by an upsetting operation andarranged totraverse said resistance element upon rotation of said shaft, an offsetportion on said wiper adjacent to said shaft comprising a plurality ofdepending legs, a terminal on said base and a spring arm having one endfixedV to saidbase, the

opposite end of said arm being held by its resiliency firmly inimmediatel electrical engagement with said depending legs of said Wiper,said engaging portions of said Wiper and said arm being located on thesaine side of said base'and said arm cooperating With said dependinglegs to prevent longitudinal movement of said shaft.

5. In a rlieostat, a supporting base, aresistance element mountedon saidbase, a shaft rotatably supported by 'said base, a Wiper secured to saidshaft by an upsetting operation and arranged to traverse saidresistance` acting frictionally to retain said Wiper Yin* its adjustedpositions, said arm andwiper cooperating to prevent longitudinalmovement of said shaft; v j' 5 i 6. In a rlieostat, a supporting base, aring shapedA resistance elementv secured to said base, a terminalsecured to said base, a hub integral with the base, a shaft rotatablymounted in said hub, a resilient conducting member having one endsecured to said terminal and its other end loosely v4fitted on the saidvsaidshaft having vareduced end portion, av

Wiper supportedvon said reduced portion by upsetting theend of 'saidreduced portion,

said Wiper arranged to'traverse said resist-i ance elementl onrotationof said shaft, said `Wiper having an enlarged portion comprisinga plurality of depending legs, said conducting member being resilientlyrheld in immediate electrical engagement with the said Wiper,

said engaging portions of said armand Wiper being located on the sameside ofV said hub ,l member and serving as means' to preventlongitudinal movement of said shaft.

, 7. In a rheostat, a supportingl base, av ring shaped resistanceVelement secured at its ends to said base, a terminalsecured to saidbase, a hub integral WithA said bas`e,a shaft having a reduced endport-ion rotatably 'mounted in said hub, ,aresilient arm of conductinginaterial, one end of whichis secured to' said terminal and they otherend of'which is loosely fitted about said shaft, a Wiper lhaving an en*ylarged portion comprising a plurality ofde-y `pending legs, saidreduced end of said shaft beingspun over to secure said Wiper to saidshaft, one end of said Wiper engaging said resistance coil, an armsecured to said reduced Aend of said shaft having depending legs whichengage the said Wiper on opposite sides to assure the rotation of saidWiper, said re-r silient 'arm having an enlarged portion adapted toengage the said plurality of depending legs on said Wiper, said engagingportions of said resilient arm and Wiper being located. on the saineside of said hub.

8. Ina rheostat, a supporting base, a`ring shaped resistance elementsecured to said base, a'terininal secured to said base, a hub integralwith said base,a sleeve extending through said hub and beingself-sustained therein, a rotatable shaft having a reduced Wiper adaptedto engage said resistance element and having an enlarged'portioncomprising a plurality of split portions, said ref duced end of saidshaft being upset to secure 'said Wiper to said shaft, and cause thesaineV to rotate, an arm secured to said shaft having depending legswhich engage said Wiper on opposite edges thereof to assure the rotationof said Wiper, said resilient arm and said split portions of said Wiperadapted to engage each other, said resiliency of said conducting inembermaintaining contactual `engagement of l.said Wiper and saidv conductingmember.

k9,' A deviceof the character described in-v end portion extendingthrough saidy sleeve, a i resilientfconducting member having one of 'itsends secured to said terminal, and its i iic other end looselyy fittedaround said shaft, a v

cluding a supporting base, a ring shaped resistance element secured tosaid hase, a terminal secured to said base, a hub integral With saidbase, a sleeve extending throughsaid hub and being self sustainingtherein, a rotatable sha-ft extending through said Sleeve and having areduced end portion, a spring arm of conducting material, one endofwhich is fixed to Said base and the other end of which is enlarged andloosely fitted about said Shaft, a Wiper adapted to engage saidresistance element, said reduced end of said shaft being Spun over torigidly secure said wiper to said shaft, depending legs integrallyformed with Said Wiper adapted to be engaged by the enlarged end of saidarm which is interposed between Said depending legs of said Wiper andthe hub portion of said base, said arm ovuerating electrically to joinsaid Wiper to said terminal and also provide friction means Jforn'aintztining said Wiper in any of its adj usted positions and forpreventing longitudinal movement oi Said shaft.

In testimony whereof I have Signed this Speciieation.

ERNEST A. BOHLMAN.

